This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A131533 #28 Dec 12 2023 09:36:34
%S A131533 0,0,0,0,1,-1,0,0,0,0,1,-1,0,0,0,0,1,-1,0,0,0,0,1,-1,0,0,0,0,1,-1,0,0,
%T A131533 0,0,1,-1,0,0,0,0,1,-1,0,0,0,0,1,-1,0,0,0,0,1,-1,0,0,0,0,1,-1,0,0,0,0,
%U A131533 1,-1,0,0,0,0,1,-1,0,0,0,0,1,-1,0,0,0,0,1,-1,0,0,0,0,1,-1,0,0,0,0,1,-1,0,0,0,0,1,-1,0,0
%N A131533 Period 6: repeat [0, 0, 0, 0, 1, -1].
%H A131533 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (-1,-1,-1,-1,-1).
%F A131533 G.f.: x^4/((x+1)*(x^2+x+1)*(x^2-x+1)). - _R. J. Mathar_, Nov 14 2007
%F A131533 a(n) = - cos(Pi*n/3)/3 + sin(2*Pi*n/3)/sqrt(3) + (-1)^n/3. - _R. J. Mathar_, Oct 08 2011
%F A131533 a(n) + a(n-1) + a(n-2) + a(n-3) + a(n-4) + a(n-5) = 0 for n>4. - _Wesley Ivan Hurt_, Jun 20 2016
%p A131533 A131533:=n->[0, 0, 0, 0, 1, -1][(n mod 6)+1]: seq(A131533(n), n=0..100); # _Wesley Ivan Hurt_, Jun 20 2016
%t A131533 PadRight[{}, 108, {0,0,0,0,1,-1}] (* _Harvey P. Dale_, Jan 27 2012 *)
%o A131533 (PARI) a(n)=[0,0,0,0,1,-1][n%6+1] \\ _Charles R Greathouse IV_, Jun 02 2011
%o A131533 (Magma) &cat [[0, 0, 0, 0, 1, -1]^^20]; // _Wesley Ivan Hurt_, Jun 20 2016
%K A131533 sign,easy,less
%O A131533 0,1
%A A131533 _Paul Curtz_, Aug 26 2007
%E A131533 Edited by _N. J. A. Sloane_, Sep 15 2007